A Schmitt trigger circuit finds a variety of practical application for its hysteresis loop of input-output voltage characteristics. In some applications, the hysteresis range is directly concerned in the circuit behavior, so that it is advantageous to have a construction capable of precisely adjusting the hysteresis range. When a Schmitt trigger circuit is employed in a logic circuit, the Schmitt trigger circuit is expected to operate at a faster switching speed.
It is therefore an important object of the present invention to provide a Schmitt trigger circuit which has a construction capable of precisely adjusting the hysteresis range and performing at an improved switching speed.